Theory and validation of access flow measurement by dilution technique during hemodialysis

Access blood flow is currently measured by color-coded duplex sonography which has the ability to select groups of patients with higher risk of access failure [1]. There are also reports of operator errors [2] and of precision limitations arising from random uncertainties in the measurement of vessel diameter and Doppler angle [3]. Color-coded duplex sonography is an expensive technique and measurements are made only rarely. The onset of reduced flow can therefore be missed. We recently reported a modification of the indicator dilution method for measuring access flow during hemodialysis [4] and the initial clinical use of this method [5]. This paper presents the theory and bench validation for this new access flow measurement technique.